1. Field of the Invention
This invention relates to electronic circuits, and more particularly, to circuits configured to monitor power supply noise.
2. Description of the Related Art
The stability of a power supply voltage is essential for the proper operation of many electronic systems. An unstable power supply voltage can cause erroneous operation that may lead to unrecoverable errors. Due to the importance of power supply stability, many integrated circuits (IC's) include power monitoring circuits configured to detect power supply noise.
Various types of detection circuits may be implemented in order to detect power supply noise. Once such type of circuit is a ring oscillator. Some ring oscillators may vary the frequency of a respective output signal responsive to a spike (i.e. increase) in the power supply voltage. Ring oscillators may also be designed to vary the frequency of a respective output signal responsive to a droop (i.e. decrease) in the power supply voltage. In either case, the variation in the output frequency may be measured by detecting jitter in the output signal.
Another type of noise detector circuit may utilize a comparator to compare the power supply voltage to a reference voltage. If the reference voltage can be controlled to a sufficient degree of precision, power supply noise may be detected and indicated by the comparator.